Tool for dressing grinding wheels and the like

ABSTRACT

A tool for dressing and trueing abrasive grinding wheels. The tool includes a matrix in the shape of a rectangular prism formed of fused powdered metal removably held in a holder, and a plurality of diamond macles imbedded in the matrix. The matrix has a rectangular front face with end edges that engage the grinding wheel, the top face being progressively eroded during the dressing operation. The macles are located with their faces perpendicular to the direction of movement of the grinding wheel surface and with one point thereof at an end edge of the front face of the matrix, so that even though the matrix and macles are eroded during the dressing operation, a diamond point is always maintained at each end edge of the front face.

United States Patent [191 Cirell et al.

[451 Feb. 12, 1974 TOOL FOR DRESSING GRINDING WHEELS AND THE LIKE 22 Filed: Jan. 19, 1972 21 Appl. No.: 219,015

[52] US. Cl. 125/11 R, 125/39 [51] Int. Cl B24b 53/12 [58] Field of Search.. 125/11 R, 11 CW, 11 DF, 38,

OTHER PUBLICATIONS Long, Albert and Slawson, Bureau of Mines Report of Investigation 4853, Diamond Orientation in Diamond Bits, Feb. 1952 page 6 and FIG. 11.

Primary Examiner-Harold D. Whitehead Assistant ExaminerNicholas P. Godici [5 7] ABSTRACT A tool for dressing and trueing abrasive grinding wheels. The tool includes a matrix in the shape of a rectangular prism formed of fused powdered metal removably held in a holder, and a plurality of diamond macles imbedded in the matrix. The matrix has a rectangular front face with end edges that engage the grinding wheel, the top face being progressively eroded during the dressing operation. The macles are located with their faces perpendicular to the direction of movement of the grinding wheel surface and with one point thereof at an end edge of the front face of the matrix, so that even though the matrix and macles are eroded during the dressing operation, a diamond point is always maintained at each end edge of the front face.

1 Claim, 8 Drawing Figures PATENTED FEB 1 21924 3.79136? TOOL FOR DRESSING GRINDING WHEELS AND THE LIKE SUMMARY OF THE INVENTION This invention relates to the periodic dressing and trueing of abrasive grinding wheels formed of silicon carbide, aluminum oxide, or other abrasive material and especially to a dressing tool with industrial diamonds carried thereby for cutting and renewing the surface of the abrasive material as the tool is traversed back and forth across the revolving grinding surface of the turning wheel. More particularly the invention relates to a tool head and the shape, orientation and means for supporting the industrial diamonds carried by the tool head.

In conventional grinding operations it is necessary to periodically dress the surface of abrasive grinding wheels in order to true the surface, to remove metal particles that clog the pores of the abrasive material and to renew the sharp cutting edge of the wheel. The dressing operation often takes as long as fifteen minutes and the frequency of periodic redressing significantly affects the number of operations that may be performed by a wheel over a given period of time as well as the quality of the surface of the workpiece to be ground and the percentage of rejected workpieces. Accordingly, the dressing or redressing operation is extremely important in grinding operations.

One of the more popular types of dressing tools currently used in the grinding art is referred to as the diamond grit tool. This tool has a cutting head in the form of a solid block or matrix that is brazed or soldered onto one end of a tool holder. The matrix contains diamonds, usually small industrial diamonds referred to as diamond grit. The grit is mixed into a quantity of comminuted fusable metal particles and the mixture is poured into a mold according to powdered metallurgy practices well known in the art and heated to fuse the particles. The solid block or matrix is removed from the mold and soldered in place on the end of a tool holder which is typically formed of round bar stock about 7/16 inch in diameter. The fused metal is progressively eroded or ground away during dressing operations and typically from 10 to diamond grits are exposed to a grinding wheel surface at one time. As the tool face wears other diamonds progressively emerge at the surface.

One principal disadvantage of this type of tool is that it is unsatisfactory for what is referred to as contour dressing. ln contour grinding wheels, the abrasive surface of the grinding wheel has a contoured form or shape in order to grind the complimentary form in the workpiece. If a dressing tool is to follow a curved contour in the face of the wheel, the tool must be in constant contact with the abrasive material as it traverses back and forth across the grinding surface. Normally the dressing tool traverses back and forth from right to left and left to right so that only one edge or corner is in cutting contact with the wheel. Because of the random distribution of diamond grit in the matrix for a diamond grit dressing tool, it is impossible for the tool to hold its edge and it will wear away in one pass or traverse.

Another type of tool used in the prior art is referred to as a cluster tool. The tool head for this type of tool is usually round and has a plurality of large diamonds rather than diamond grit embedded in a matrix of fused powdered metal. The principal disadvantages of this tool are that (1) it also cannot be used for dressing form or contour type grinding wheels, (2) it generates considerable heat and (3) the diamonds upon erosion become blunt or dull so that the tool merely burnishes or polishes the wheel surface.

In summary the principal disadvantages of dressing tools of the prior art are:

l. The number of pieces ground between wheel dressing and redressing operations is too low.

2. The cost of replacing a dressing tool is high.

3. The dressing tool must be periodically returned to a tool manufacturer to have the diamonds reset to new points. This necessitates maintaining a rather large inventory of dressing tools in order to accomodate the continual resetting of tools by the manufacturer.

4. Different types of dressing tools are needed for different types of wheels, no one single tool being suitable for several different types of wheels such as for dressing special wheels for contour grinding, form grinding, O.D. grinding and centerless grinding.

5. Too many rejected workpieces are ground due to poorly dressed wheels.

6. Too much tapering of the tool head (e.g. matrix) at the corners or edges.

7. Too much operator time is required in the dressing operation resulting in excessive downtime for the grinding wheel.

8. Present dressing tools require a high level of operator skill.

9. Too many dressing tools must be kept in inventory.

The device of the present invention, however, reduces the difficulties indicated above and affords other features and advantages heretofore not obtainable.

SUMMARY OF THE INVENTION It is among the objects of the present invention to reduce the cost of dressing the trueing abrasive grinding wheels.

Another object is to reduce the time and operator skill required for the dressing and trueing of abrasive grinding wheels.

Still another object is to increase the versatility as to the types of dressing and trueing operations that may be performed on various types of abrasive grinding wheels by a single dressing tool.

A further object is to improve the quality and consistancy of dressing and trueing operations on abrasive grinding wheels by a matrix-type diamond dressing tool head.

A still further object is to increase the useful life of abrasive grinding wheels by improving the quality of the periodic dressing and trueing thereof.

These and other objects are accomplished by the novel dressing tool construction of the present invention, wherein the tool includes a novel cutting block or matrix carried by a tool support for traversing movement while in cutting engagement with the grinding face of an abrasive wheel. The matrix is a solid block generally in the shape of a rectangular prism with a wheel-engaging front face, parallel top and bottom faces parallel to the wheel axis and parallel end faces perpendicular to the wheel axis. It is conventionally formed of heat fused comminuted metal according to conventional powdered metallurgy practices. A plurality of diamond macles (natural diamonds in the form of thin, flat, triangular crystals with two parallel triangular planar faces and three narrow side edges that meet at the corner points) are imbedded in the matrix with their faces in planes generally parallel to the top and bottom faces of the matrix, one side edge in an end face and one point at an edge of the wheel-engaging front face. The macles are most commonly in the form of an equilateral triangle and the point of the macle in the front face is continuously positioned for cutting engagement with the grinding wheel surface throughout the progressive erosion of the front face.

According to the preferred form of the invention macles are imbedded adjacent both end faces of the matrix so that both end edges of the front face have diamond cutting points to contact the wheel surface regardless of the contour of the dressing wheel and regardless of the direction of traverse of the tool laterally across the surface of the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view on an enlarged scale (about three times actual size) of a portion of a dressing tool embodying the invention;

FIG. 2 is a fragmentary side elevation on a reduced scale of an abrasive grinding wheel being dressed and trued by the dressing tool of FIG. 1;

FIG. 3 is a fragmentary plan view of the grinding wheel and dressing tool of FIG. 2;

FIG. 4 is a fragmentary sectional view on an enlarged scale taken on the line 4-4 of FIG. 2;

FIG. 5 is a fragmentary sectional view similar to FIG. 4 illustrating the condition of the tool after the head has been eroded by a number of dressing operations;

FIG. 6 is a sectional view taken on the line 6-6 of FIG. 4;

FIG. 7 is an exploded perspective view on an enlarged scale illustrating the construction of the tool head or matrix embodying the invention; and

FIG. 8 is an elevational view on an enlarged scale of a modified form of dressing tool embodying the invention, the tool holder being shown in dashed lines.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly to the drawings and initially to FIGS. 13, there is shown a diamond headed dressing tool 10 adapted for dressing and trueing an abrasive grinding wheel 11 having a contoured grinding surface. The tool 10 is adapted to traverse back and forth laterally in a direction parallel to the axis of the wheel and in view of the contour of the grinding face of the wheel as illustrated in FIG. 3, the too] must be moved endwise toward and away from the wheel in order that the tool head may follow the contour of the wheel. The tool includes a bifurcated holder 12 adapted to receive and retain a tool head or matrix 13 which is conventionally soldered in place between the bifurcations 14. The matrix 13 comprises comminuted metal particles of iron or other suitable metal heat fused under pressure according to practices known in the art to form a solid block. In the embodiment shown the block is in the form of a rectangular prism with a work engaging front face 15, top and bottom faces 16 and end faces 17.

Embedded within the matrix 13 are six diamond macles 18 which are twin diamond crystals that are found in nature and which generally have a triangular form,

most commonly equilateral, with three points that provide convenient cutting edges. Macles occur in many different sizes ranging from about 1 4: karat to as small as l5 stones per karat. In accordance with the invention at least two macles are imbedded in the matrix.

The unique advantages of the invention are achieved by the manner of positioning the macles 18 within the matrix 13 all of which is accomplished during the forming and fusing of the powdered metal. The positioning of the macles 18 is best illustrated in FIGS. 4-7 and it will be seen that the faces thereof are all in planes parallel to the top and bottom faces 16. Three of the macles are positioned adjacent each end face 17 of the matrix 13' and one side thereof is located in the respective end face 17 with one point thereof at the respective end edge of the front face or cutting face 15. The three macles on each side are preferably uniformly spaced and the macles at one end face are each spaced between adjacent macles on the opposite end face as best illustrated in FIG. 6. The height of the triangular macles is greater than half the side dimension of the matrix so that the interior points overlap one another. With this arrangement six diamond points are always provided at the end edges of the cutting face 15.

FIG. 5 illustrates the unique advantages obtained with the dressing tool construction of the invention, particularly in connection with the condition of the matrix after substantial erosion of the front face has occurred due to a considerable period of dressing, all of which serves to progressively and continuously remove material from the matrix. It will be noted that although the erosion flattens out the respective points that initially lie in the front face 15 so that the macles take on a quadlilateral form, a diamond point is still located at each end corner or edge of the front face 15. These points will engage and cut the abrasive material of the grinding wheel 11 during the left-to-right and right-toleft traversing of the tool during the dressing operation so that a diamond will be continuously exposed.

FIG. 8 illustrates a modified form of the invention wherein a dressing tool 20 having a holder 21. and a fused metal matrix 22 is provided with ten macles including six macles 23 positioned with one point thereof in the cutting surface and four macles 24 in a position with their uppermost points spaced below the initial cutting surface so that their points will not be exposed until substantial erosion of the cutting face has taken place. Many other configurations or relative locations of macles in the matrix may be employed depending upon the particular application. The principal consideration according to the invention is that macles be positioned with one point initially in the cutting surface at opposite ends of the cutting face and located with one side edge in the end face so that a diamond point is continuously exposed to the abrasive material during dressing throughout the life of the matrix. Also it will be noted that in the embodiment shown, the erosion of up to 50 percent of the overall depth of the matrix can be accoi'nmodat ed before the matrix need be replaced.

It will be apparent that with the dressing tool construction of the invention, a relatively large number of dressing operations can be performed without replacing the matrix and the same tool can be used for many types of dressing operations such as to dress contour grinding wheels as illustrated, straight wheels, O.D. grinding wheels, centerless grinding wheels, etc. Also because diamond points are continuously presented to the grinding surface the wearing down of the diamond crystal does not burnish or polish the abrasive grinding wheel surface and does not blunt the wheel or leave minute metal particles in the pores of the wheel surface.

While the invention has been shown and describedwith respect to specific embodiments thereof this is intended for the purpose of illustration rather than limitation and other variations and modifications of the specific forms herein shown and described will be apparent to those skilled in the art upon a reading of the specification all within the intended spirit and scope of the invention. Accordingly the patent is not to be limited to the specific embodiments herein shown and described nor in any other way that is inconsistant with the extent to which the progress in the art has been advanced by the invention.

We claim:

1. In a dressing tool adapted to traverse across the face of a rotating abrasive grinding wheel, the tool including a holder that supports a solid matrix having a wheel-engaging front face with end edges perpendicular to the direction of traverse, top and bottom faces generally parallel to the direction of traverse, and end faces generally perpendicular to the direction of traverse, the improvement which comprises:

a plurality of macles embedded in said matrix, said macles comprising natural diamonds in the form of thin, flat triangular crystals with two parallel triangular planar faces and three narrow side edges that meet at the corners to define points, said macles being mounted in said matrix with their planar faces generally parallel to said top and bottom faces of said matrix, with one side edge of each macle in one of said end faces of said matrix and with one point in said front face at one of said end edges of said front face,

whereby as said front face is eroded during dressing said macles each continuously have a point in the respective end edge defined at the intersection of said front face and the respective end face. 

1. In a dressing tool adapted to traverse across the face of a rotating abrasive grinding wheel, the tool including a holder that supports a soliD matrix having a wheel-engaging front face with end edges perpendicular to the direction of traverse, top and bottom faces generally parallel to the direction of traverse, and end faces generally perpendicular to the direction of traverse, the improvement which comprises: a plurality of macles embedded in said matrix, said macles comprising natural diamonds in the form of thin, flat triangular crystals with two parallel triangular planar faces and three narrow side edges that meet at the corners to define points, said macles being mounted in said matrix with their planar faces generally parallel to said top and bottom faces of said matrix, with one side edge of each macle in one of said end faces of said matrix and with one point in said front face at one of said end edges of said front face, whereby as said front face is eroded during dressing said macles each continuously have a point in the respective end edge defined at the intersection of said front face and the respective end face. 